Documentation/driver-api/cxl: remove page-allocator quirk section

The node/zone quirk section of the cxl documentation is incorrect.
The actual reason for fallback allocation misbehavior in the
described configuration is due to a kswapd/reclaim thrashing scenario
fixed by the linked patch.  Remove this section.

Link: https://lore.kernel.org/linux-mm/20250919162134.1098208-1-hannes@cmpxchg.org/
Signed-off-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

diff --git a/Documentation/driver-api/cxl/allocation/page-allocator.rst b/Documentation/driver-api/cxl/allocation/page-allocator.rst
index 7b8fe1b8d5bbb831e4363ab48d696e6aa81f8e72..3fa584a248bdd3651af1f51855c701997931cba7 100644 (file)
--- a/Documentation/driver-api/cxl/allocation/page-allocator.rst
+++ b/Documentation/driver-api/cxl/allocation/page-allocator.rst
@@ -41,37 +41,6 @@ To simplify this, the page allocator will prefer :code:`ZONE_MOVABLE` over
 will fallback to allocate from :code:`ZONE_NORMAL`.
 
 
-Zone and Node Quirks
-====================
-Let's consider a configuration where the local DRAM capacity is largely onlined
-into :code:`ZONE_NORMAL`, with no :code:`ZONE_MOVABLE` capacity present. The
-CXL capacity has the opposite configuration - all onlined in
-:code:`ZONE_MOVABLE`.
-
-Under the default allocation policy, the page allocator will completely skip
-:code:`ZONE_MOVABLE` as a valid allocation target.  This is because, as of
-Linux v6.15, the page allocator does (approximately) the following: ::
-
-  for (each zone in local_node):
-
-    for (each node in fallback_order):
-
-      attempt_allocation(gfp_flags);
-
-Because the local node does not have :code:`ZONE_MOVABLE`, the CXL node is
-functionally unreachable for direct allocation.  As a result, the only way
-for CXL capacity to be used is via `demotion` in the reclaim path.
-
-This configuration also means that if the DRAM ndoe has :code:`ZONE_MOVABLE`
-capacity - when that capacity is depleted, the page allocator will actually
-prefer CXL :code:`ZONE_MOVABLE` pages over DRAM :code:`ZONE_NORMAL` pages.
-
-We may wish to invert this priority in future Linux versions.
-
-If `demotion` and `swap` are disabled, Linux will begin to cause OOM crashes
-when the DRAM nodes are depleted. See the reclaim section for more details.
-
-
 CGroups and CPUSets
 ===================
 Finally, assuming CXL memory is reachable via the page allocation (i.e. onlined